Gracie Burke is a 7-year-old Labrador retriever, and house-call patient of mine. Her owners were concerned when, a few days after they returned from a trip, she was acting lethargic and weak, breathing quickly and not eating. Gracie loved to go for walks, and now didn't want to get off the couch.
I immediately noticed that her gums were pale and her heart was beating abnormally fast. Their college-aged son had been watching her while they were away, and he said he was certain that she did not get into anything unusual while in his care.
Blood work revealed severe anemia, and further analysis specified that she had Heinz bodies and methemoglobinemia, both specific changes of red blood cell destruction. It was possible she had ingested something toxic such as zinc, moth balls, onion, or garlic. Another possibility was that she developed immune-mediated hemolytic anemia, in which case, the animal's own immune system attacks and destroys red blood cells. Treatments for these two conditions are completely different, so identifying the cause was critical.
Gracie was so anemic that she was dangerously close to needing a blood transfusion. What was causing her problems?
Further testing revealed that the cause was not immune-mediated. We needed to determine what, if anything, Gracie could have eaten that could account for her anemia.
Of the possible culprits, onions or garlic were the only things that might have been found in the home. Her owners' son insisted that he had not cooked with onions or garlic for the two weeks his parents were away. For that matter, he had basically ordered takeout the entire time.
But it turned out that the son had been hosting nightly get-togethers with friends, and served beer and chips. Evidently, Gracie had enjoyed two weeks of nachos and onion dip. The cause of her anemia was onion toxicosis.
Onions and garlic, both in the allium family, are dangerous to dogs and cats because they lack a protective enzyme in their red blood cells that wards off oxidant-induced injury caused by onions.
If she had had just a small amount, Gracie's body would have responded by making new blood cells. But her nightly onion dip was enough to produce a life-threatening anemia.
Different onions and garlic varieties have different levels of toxicity, but generally the stronger the odor and flavor, the greater the danger. There are several varieties of toxic compounds in onions, some of which form only after chopping, heating, or during digestion. The dip that Gracie got into contained small dried-onion chunks.
The amounts were small, but the effect accumulated over time, explaining why the symptoms didn't become obvious for a few days after the parties ended.
Gracie needed a transfusion and oxygen therapy, but recovered after several days of hospitalization. She is back to her normal self, and is off the onion dip.